/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package qunar.tc.bistoury.instrument.client.spring.el;

import org.objectweb.asm.MethodVisitor;

import java.math.BigDecimal;
import java.math.BigInteger;

/**
 * The plus operator will:
 * <ul>
 * <li>add numbers
 * <li>concatenate strings
 * </ul>
 *
 * <p>It can be used as a unary operator for numbers.
 * The standard promotions are performed when the operand types vary (double+int=double).
 * For other options it defers to the registered overloader.
 *
 * @author Andy Clement
 * @author Juergen Hoeller
 * @author Ivo Smid
 * @author Giovanni Dall'Oglio Risso
 * @since 3.0
 */
class OpPlus extends Operator {

    public OpPlus(int pos, SpelNodeImpl... operands) {
        super("+", pos, operands);
        Assert.notEmpty(operands, "Operands must not be empty");
    }


    @Override
    public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
        SpelNodeImpl leftOp = getLeftOperand();
        SpelNodeImpl rightOp = getRightOperand();

        if (rightOp == null) {  // if only one operand, then this is unary plus
            Object operandOne = leftOp.getValueInternal(state).getValue();
            if (operandOne instanceof Number) {
                if (operandOne instanceof Double) {
                    this.exitTypeDescriptor = "D";
                } else if (operandOne instanceof Float) {
                    this.exitTypeDescriptor = "F";
                } else if (operandOne instanceof Long) {
                    this.exitTypeDescriptor = "J";
                } else if (operandOne instanceof Integer) {
                    this.exitTypeDescriptor = "I";
                }
                return new TypedValue(operandOne);
            }
            return state.operate(Operation.ADD, operandOne, null);
        }

        TypedValue operandOneValue = leftOp.getValueInternal(state);
        Object leftOperand = operandOneValue.getValue();
        TypedValue operandTwoValue = rightOp.getValueInternal(state);
        Object rightOperand = operandTwoValue.getValue();

        if (leftOperand instanceof Number && rightOperand instanceof Number) {
            Number leftNumber = (Number) leftOperand;
            Number rightNumber = (Number) rightOperand;

            if (leftNumber instanceof BigDecimal || rightNumber instanceof BigDecimal) {
                BigDecimal leftBigDecimal = NumberUtils.convertNumberToTargetClass(leftNumber, BigDecimal.class);
                BigDecimal rightBigDecimal = NumberUtils.convertNumberToTargetClass(rightNumber, BigDecimal.class);
                return new TypedValue(leftBigDecimal.add(rightBigDecimal));
            } else if (leftNumber instanceof Double || rightNumber instanceof Double) {
                this.exitTypeDescriptor = "D";
                return new TypedValue(leftNumber.doubleValue() + rightNumber.doubleValue());
            } else if (leftNumber instanceof Float || rightNumber instanceof Float) {
                this.exitTypeDescriptor = "F";
                return new TypedValue(leftNumber.floatValue() + rightNumber.floatValue());
            } else if (leftNumber instanceof BigInteger || rightNumber instanceof BigInteger) {
                BigInteger leftBigInteger = NumberUtils.convertNumberToTargetClass(leftNumber, BigInteger.class);
                BigInteger rightBigInteger = NumberUtils.convertNumberToTargetClass(rightNumber, BigInteger.class);
                return new TypedValue(leftBigInteger.add(rightBigInteger));
            } else if (leftNumber instanceof Long || rightNumber instanceof Long) {
                this.exitTypeDescriptor = "J";
                return new TypedValue(leftNumber.longValue() + rightNumber.longValue());
            } else if (CodeFlow.isIntegerForNumericOp(leftNumber) || CodeFlow.isIntegerForNumericOp(rightNumber)) {
                this.exitTypeDescriptor = "I";
                return new TypedValue(leftNumber.intValue() + rightNumber.intValue());
            } else {
                // Unknown Number subtypes -> best guess is double addition
                return new TypedValue(leftNumber.doubleValue() + rightNumber.doubleValue());
            }
        }

        if (leftOperand instanceof String && rightOperand instanceof String) {
            this.exitTypeDescriptor = "Ljava/lang/String";
            return new TypedValue((String) leftOperand + rightOperand);
        }

        if (leftOperand instanceof String) {
            return new TypedValue(
                    leftOperand + (rightOperand == null ? "null" : convertTypedValueToString(operandTwoValue, state)));
        }

        if (rightOperand instanceof String) {
            return new TypedValue(
                    (leftOperand == null ? "null" : convertTypedValueToString(operandOneValue, state)) + rightOperand);
        }

        return state.operate(Operation.ADD, leftOperand, rightOperand);
    }

    @Override
    public String toStringAST() {
        if (this.children.length < 2) {  // unary plus
            return "+" + getLeftOperand().toStringAST();
        }
        return super.toStringAST();
    }

    @Override
    public SpelNodeImpl getRightOperand() {
        if (this.children.length < 2) {
            return null;
        }
        return this.children[1];
    }

    /**
     * Convert operand value to string using registered converter or using
     * {@code toString} method.
     *
     * @param value typed value to be converted
     * @param state expression state
     * @return {@code TypedValue} instance converted to {@code String}
     */
    private static String convertTypedValueToString(TypedValue value, ExpressionState state) {
        TypeConverter typeConverter = state.getEvaluationContext().getTypeConverter();
        TypeDescriptor typeDescriptor = TypeDescriptor.valueOf(String.class);
        if (typeConverter.canConvert(value.getTypeDescriptor(), typeDescriptor)) {
            return String.valueOf(typeConverter.convertValue(value.getValue(),
                    value.getTypeDescriptor(), typeDescriptor));
        }
        return String.valueOf(value.getValue());
    }

    @Override
    public boolean isCompilable() {
        if (!getLeftOperand().isCompilable()) {
            return false;
        }
        if (this.children.length > 1) {
            if (!getRightOperand().isCompilable()) {
                return false;
            }
        }
        return (this.exitTypeDescriptor != null);
    }

    /**
     * Walk through a possible tree of nodes that combine strings and append
     * them all to the same (on stack) StringBuilder.
     */
    private void walk(MethodVisitor mv, CodeFlow cf, SpelNodeImpl operand) {
        if (operand instanceof OpPlus) {
            OpPlus plus = (OpPlus) operand;
            walk(mv, cf, plus.getLeftOperand());
            walk(mv, cf, plus.getRightOperand());
        } else {
            cf.enterCompilationScope();
            operand.generateCode(mv, cf);
            if (!"Ljava/lang/String".equals(cf.lastDescriptor())) {
                mv.visitTypeInsn(CHECKCAST, "java/lang/String");
            }
            cf.exitCompilationScope();
            mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
        }
    }

    @Override
    public void generateCode(MethodVisitor mv, CodeFlow cf) {
        if (this.exitTypeDescriptor == "Ljava/lang/String") {
            mv.visitTypeInsn(NEW, "java/lang/StringBuilder");
            mv.visitInsn(DUP);
            mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "()V", false);
            walk(mv, cf, getLeftOperand());
            walk(mv, cf, getRightOperand());
            mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);
        } else {
            getLeftOperand().generateCode(mv, cf);
            String leftDesc = getLeftOperand().exitTypeDescriptor;
            CodeFlow.insertNumericUnboxOrPrimitiveTypeCoercion(mv, leftDesc, this.exitTypeDescriptor.charAt(0));
            if (this.children.length > 1) {
                cf.enterCompilationScope();
                getRightOperand().generateCode(mv, cf);
                String rightDesc = getRightOperand().exitTypeDescriptor;
                cf.exitCompilationScope();
                CodeFlow.insertNumericUnboxOrPrimitiveTypeCoercion(mv, rightDesc, this.exitTypeDescriptor.charAt(0));
                switch (this.exitTypeDescriptor.charAt(0)) {
                    case 'I':
                        mv.visitInsn(IADD);
                        break;
                    case 'J':
                        mv.visitInsn(LADD);
                        break;
                    case 'F':
                        mv.visitInsn(FADD);
                        break;
                    case 'D':
                        mv.visitInsn(DADD);
                        break;
                    default:
                        throw new IllegalStateException(
                                "Unrecognized exit type descriptor: '" + this.exitTypeDescriptor + "'");
                }
            }
        }
        cf.pushDescriptor(this.exitTypeDescriptor);
    }

}
